The invention relates to a powder metering apparatus for making available powder, in particular for powder coating.
EP 0 412 289 B1 discloses an electrostatic powder coating device, wherein an injector pump delivers coating powder by means of a conveying gas, and wherein an additional metered gas line from a source of compressed air connects to the injector pump. The metered gas line, via which metered gas is supplied to the injector pump, is intended to facilitate adjustment of the amount of conveying air and the amount of metered air to optimal values. While the introduction of metered gas into the injector pump improves controllability of an injector pump with respect to supplying a desired quantity of powder needed in particular for coating, controllability and thus metering capability of the powder quantity do however not reach the accuracy of conventional, rotatably driven metering pumps of the disk type.
DE 4 242 225 A1 discloses a powder varnish pump for producing and metering a powder, which flows under overpressure. In the described powder varnish pump, the actual feed pump is designed and constructed as a metering pump of the disk type. In this pump, one metering disk is arranged for rotation between lateral components. The metering disk has an inlet, which receives a powder-air mixture, and an outlet, which supplies the powder-air mixture to a consumer, i.e., the described coating purpose. The discharge of the powder-air mixture from the outlet of the metering pump occurs by means of compressed air. As a result of the compressed air, it is possible that powder deposits in the interior of the outlet chamber and in particular in the sealing points between the rotating metering disk and the stationary lateral components. The deposit of powder in the described areas increases the wear of the metering pump. Furthermore, the metering pump has an increased torque that may lead to a blocking of the metering pump. Likewise, there is a risk of leakage.
It is therefore the object of the invention to provide a powder metering apparatus with a metering pump known per se, which exactly meters the quantity of powder necessary for the coating, operates with little wear and high reliably, and wherein powder is largely prevented from depositing in particular in its sealing gaps.